Scroll device for compression or expansion

ABSTRACT

A device for varying pressure of a fluid comprising a scroll case ( 11 ) containing a fixed scroll ( 12 ) and a mobile scroll ( 13 ) relatively to the case, and with admission (A) and outlet (B) ports for the fluid, characterized in that it comprises means for thermally insulating the scrolls.

TECHNICAL FIELD

The present invention generally relates to a pressure variation deviceformed with a simple scroll device, of a compressor or expander type, ora scroll device including two coupled stages on a rotary shaft andpositioned at both ends of an intermediate electric power device (motoror generator). According to another aspect, the present invention moreparticularly relates to a simple scroll or two-stage scroll device withwhich an operating fluid at high temperature and/or with a high pressureratio may be expanded or compressed. According to another aspect, thepresent invention relates to a scroll device integrating a feed pump.

TECHNICAL BACKGROUND

Scroll devices which may be alternatively used as an expander or acompressor are already known and provide a certain number of advantagesin terms of operating possibilities which by far exceed those obtainedfor machines performing a reciprocal movement. This simple design wasexplained in document U.S. Pat. No. 801,182. Such a scroll deviceconsists of an expansion or compression chamber delimited by two spiralinvolutes, a fixed scroll and an orbiting scroll, placed so that theyform a series of pockets with increasing sizes. The orbiting scroll ismounted on an eccentric drive shaft, which induces an orbiting movementrather than a simple rotary movement. During the expansion process, ahigh pressure fluid is introduced into an inlet port and dischargedthrough an outlet port at a lower pressure by increasing the volume ofthe pockets and by providing mechanical power to an electric device suchas a generator coupled to the orbiting scroll. In a compression process,the electric device operates as a motor for driving the orbiting scroll,and the operating fluid is then introduced and discharged at a higherpressure owing to the decreasing volume of the pockets. The use of suchscroll devices has some advantages. Thus, for example, only a restrictednumber of mobile parts and no valve are required and the rotary movementmay be completely balanced, reducing vibrations and noise. Such scrolldevices are notably produced for refrigeration and air-conditioningapplications.

Originally, scroll devices were used for operating with fluids andrefrigerants with relatively low pressure ratios corresponding to thelimitation of an installed volume ratio. The reason is thatcompression/expansion occurs rather gradually from chamber to chamber,so that a large scroll diameter is required for producing highcompression/expansion ratios. For a given capacity, the increase in thediameter of this scroll will therefore increase the axial forcesresulting from the large surface contact area and from the high pressuredifference between the front and rear contact surfaces of the orbitingscroll. In order to increase the capacity of the scroll device whilereducing or suppressing the unbalanced axial forces, several types ofstructures with dual scroll devices have been proposed. For example, asandwich structure was proposed with orbiting scrolls facing away fromeach other on a common shaft in document U.S. Pat. No. 4,192,152, orU.S. Pat. No. 6,123,529. Although they may handle a fluid with a highpressure ratio and are capable of integrating new functions such asexpansion and compression simultaneously, such dual scroll devicessuffer from a number of drawbacks among which the additional weight ofthe orbiting scrolls and the occurrence of a large inertial load on thebearings, the consequences of which are significant limitations on therotational speed which may be attained.

Another recurrent problem with such scroll devices is the highsensitivity to temperature changes. Compression or expansion of a fluidwith a high temperature and pressure ratio is accompanied by a widetemperature distribution range resulting in deformations anddisplacements of scrolls. The latter reveal various clearances in radialand axial directions where pressure losses, leakages and energydissipation occur, reducing efficiency.

A possible approach for reducing the clearances is to anticipate andprovide means for adapting to the differential heat expansion. For thispurpose, documents U.S. Pat. No. 4,192,152 and WO 93/20342 disclosecomplex systems based on struts and on expansion bearings forcompensating axial displacements in a dual scroll device withoutproducing significant elastic forces for increasing the bearing loads.

Another approach for reducing thermal deformations is to limit thedifferential temperature during expansion/compression. Mew scrolldesigns have been proposed in order to maintain the temperaturerelatively uniform with outer heat sources. For example, document US2005/172622 reveals a complex heating structure integrated to the scrollcase in order to simultaneously heat the expanding fluid and to thenminimize the temperature difference between the fixed scroll and theorbiting scroll. However, these heating structures are prohibitivelyexpensive to manufacture. Mother example given in document US2004/172945 which shows a type of simple winding with two expansionsteps, an external heat source of which is used for heating up theoperating fluid between both steps. This arrangement contributes toreducing the temperature difference between the scrolls but remainsexpensive to manufacture owing to the fact that the rear contactsurfaces of both scrolls are made with a plurality of cooling fins whichmakes the scroll machining operation more difficult. Additionally, as itis a source of heat losses during expansion, the use of cooling finsdecreases the operating efficiency of the device.

Document U.S. Pat. No. 5,286,179 recommends certain thermal insulationingenuities applied to a scroll compressor in order to prevent heatingof the fluid by the walls of the compressor during its admission intothe cavity of the compressor. The capacity of the compressor isincreased by maintaining a higher density only if the fluid was heatedup. The insulated portions are the inlet conduits for the fluid. Withthese ingenuities, it is by no means possible to reduce the energylosses of the fluid during its compression, nor is it possible tominimize the relative thermal deformations between the volutes (scrolls)in order to reduce their clearances.

Further, environmental issues related to check for oil and fluid(refrigerant) leaks in the atmosphere are increasingly important. Withthe purpose of reducing contaminants and building a long-lived robustscroll device, as this is required for home applications, and smallindustrial equipment, hermetically sealed scroll devices have beenconsidered as replacement solutions for conventional open drive systems.The method consists of directly connecting the motor/generator to thescroll, and then to confine both of them in a gas-tight housing whichsuppresses the problems of leaks and all the maintenance required for anopen drive system.

Integrating the needs and the demands for increasing the capacity ofscroll devices, document JP 56-165701 shows a coaxial structure of ahermetic scroll device using two scroll expanders installed on a rotaryshaft on either side of an intermediate generator. Although this is acompact solution, capable of simultaneously expanding a fluid on bothsides of the generator and of using the collected gas on the lowpressure sides for cooling the electric generator, which is required forthe efficiency of the system. Nevertheless this design does not providethe sufficient characteristics and means for producing an expansion inseries with a high pressure ratio nor for handling a fluid with a hightemperature requiring a demand for additional cooling.

Document WO 01/75273 describes a system with a dual hermetic scrolldevice with a coaxial motor/generator which may integrate a coolingsystem in order to meet additional demands for cooling. These dualscroll devices are coupled with an admission gas throttle and may beactuated over a wide load range with modulation of the cooling capacity.Nevertheless, this document presents a system with many limitations interms of possible efficiency, temperature, pressure ratio and rotationalspeed. Consequently, for example, during operation of two pairs ofscrolls at a high temperature, cooling the generator will enhance thedifferential temperature between the front and rear contact surfaces ofthe orbiting scrolls, which will have the effect of increasing heatlosses and pressure leaks due to deformations and therefore the resultof substantially reducing the efficiency of the device. Also, both pairsof scrolls are not suitable for expansion or compression with two serialstages, they should only be actuated in a parallel operating mode with asame operating fluid and with a limited pressure ratio owing to the factthat the low pressure peripheral ports of the orbiting scrolls directlycommunicate with the ports of the casing (housing) via the interiorvolume of the casing. Further, the use of a gas throttle for maintaininga specific rotational speed contributes to destroying the pressure for awide range of working conditions and is therefore not effective formodulating the cooling capacity.

Moreover, other systems are known in the prior art which are applied torecovering heat or to jointly generate electricity and heat and whichprove to be difficult to reconcile with the goals of the presentinvention, and are provided here as an indication. Thus document FR 2853 016 relates to a system for using lost heat by means of the use ofan organic Rankine cycle for recovering heat from an internal combustionengine for vehicles. Nevertheless, the use of scroll devices forapplying a heat recovery system is not provided in such a system.

Document WO 02/090747 concerns a power generation system comprising aprime mover subsystem and a subsystem for using thermal energy in aRankine cycle. The subsystem for using thermal energy may comprise ahermetically sealed volute device which may expand the thermal dynamicfluid in a configuration of pairs of single or dual volutes. This systemhas the same drawbacks as in WO 01/75273 mentioned earlier. Further,this system does not provide any means for thermally insulating thevolutes or any protection against thermal deformations.

Reference may further be made to certain documents mentioning the use inpumps with a scroll device. First of all, document DE 199 53 690concerns a scroll device with a compressor stage and another expanderstage integrated into a system used in a closed loop or in an openBrayton cycle for fuel cells, the system comprising a pump forhumidifying an air conduit and lubricating the compressor, external tothe scroll device. It will be noted that the scroll device used has thesame drawbacks as in document WO 01/75273 described earlier. DocumentsWO 01/75273 or EP 1 253 323 concern a scroll device using a lubricationpump used for generating a pressure difference in order to transport alubricant to different mobile portions, of the machine.

Finally, document JP 2004 332556 concerns a one- or two-stage scrolldevice used as a vacuum pump or compressor. Consequently, none of theseapplications is intended to provide a scroll device comprising anexpander stage, a motor and using a pump for supplying the operatingfluid.

SUMMARY OF THE INVENTION

The main object of the present invention is to overcome theaforementioned drawbacks. For this purpose, a first aspect of theinvention concerns a device for varying the pressure of a fluid,comprising a scroll case containing a fixed scroll and a mobile scrollrelatively to the case, and with admission and outlet ports for thefluids, characterized in that it comprises means for thermallyinsulating the scrolls. These thermal insulation means provide reductionof the clearances and pressure losses in the device and therefore areduction in the energy losses of the fluid during its expansion, thethermal insulation means being applied around the expansion chambers.

According to an advantageous embodiment, the thermal insulation meansare provided between the fixed scroll and the corresponding scroll case.According to another advantageous embodiment, the thermal insulationmeans are provided between the mobile scroll and the orbiting bearing ofthe device. According to another advantageous embodiment, the thermalinsulation means comprise a separation disk placed at the bottom of theorbiting bearing which separates the mobile scroll from the rotatingbearing by an insulation space. Alternatively, the thermal insulationmeans may comprise an insulating material placed between the orbitingbearing and the mobile scroll.

According to another advantageous embodiment, means for preventingthermal deformations of the scrolls are provided. These means forpreventing thermal deformations are preferably formed by an expansionring introducing a local force which deforms the mobile scroll of thecorresponding stage in the direction opposite to its normal deformationdirection.

According to a second aspect, the present invention concerns a scrolldevice including two coupled stages on a rotary shaft, at both ends ofan intermediate electric power device, wherein the first stage is formedby a first pressure variation device according to the first aspect,characterized in that the second stage is formed by a second pressurevariation device with second admission and outlet ports decoupled fromthe admission and outlet ports of the first pressure variation, device,respectively. Such a scroll device ensures operating independence ofboth stages and thereby provides larger flexibility in terms ofoperating fluids, of connection between the stages and the electricpower device and between the stages themselves. Preferably the secondpressure variation device is also a pressure variation device accordingto the first aspect.

According to an advantageous embodiment, the stage is fixed in a scrollcase and a transmission system is fixed in a transmission case andthermal insulation means are provided between the stage and thetransmission system, in the form of an insulation plate placed betweenthe scroll case and the transmission case.

According to an advantageous embodiment, the second pressure variationdevice is connected; in a series configuration to the first stage sothat one of the two stages operates at a higher pressure than the otherone. Thus, with such device, it is possible to expand or compress anoperating fluid with an extremely high pressure ratio. Advantageously,both pressure variation devices are expanders so that the first stageoperates at a high pressure of a fluid and the second stage operates ata low pressure of the same fluid. Thus, during the expansion process,the high pressure gas of the fluid flows through the inlet port into theopen chamber of the scrolls of the high pressure stage, is expanded anddelivered by the outlet port at an intermediate or medium pressure.After being collected, the half-pressurized gas is introduced into theinlet port, of the low pressure stage and is discharged through theoutlet port of this same stage after the second expansion at a towerpressure.

According to another advantageous embodiment, the second stage isconnected to the first stage, in a parallel configuration, so that thetwo pressure variation devices are independent of each other. With sucha device it is possible to treat a high capacity, both stages beingindependently operated with different operating fluids. In this case,one stage operates with an operating fluid whereas the other stageoperates with another operating fluid under different conditions.

According to a third aspect, the present invention concerns a scrolldevice comprising two coupled stages on a rotary shaft, at both ends ofan intermediate electrical power device, wherein the first stage isformed by a first pressure variation device according to the firstaspect, and characterized in that the second stage is a feed pump whichpumps the operating liquid (refrigerant) and provides it in return. Sucha device is advantageous because the operating conditions of a scrollturbine and of a feed pump are of the same order and thus by a suitableselection of the capacities of these machines (that of the pressurevariation stage and that of the pump stage) they may be coupled on asame shaft, while providing optimum efficiency of each of thesemachines. This configuration is further much less complex than aconfiguration with coupling through a transmission chain and a shaftseal or as compared with the use of two separate entities, one having agenerator and the other an electric motor. The proposed simplifieddevice according to this aspect of the invention also allowssimplification of the control system and of the hydraulic and electricconnections. It will further be noted that all the moving parts able togenerate power (pump, turbine and electricity generator) may becontained in a hermetic enclosure without any shaft seal. Thus theproblems of using inflammable, toxic fluids or harmful for theenvironment are focused on a single machine, the enclosure of whichshould be guaranteed to be hermetic, without any shaft seal between theenclosure containing the fluid and the outside.

Advantageously, the device is organized in a Rankine cycle comprising anevaporator or (a vapor generator of an operating fluid) and, a condenserof the same fluid. The vapor generator then provides the first stagewith pressurized vapor flow, which is expanded and then transmitted tothe condenser feeding the pump which pumps the liquid at the initialpressure and provides it in return to the vapor generator. This type ofdevice can be particularly used for automotive applications for instanceexhaust heat power regeneration) or for the combined production ofelectricity and heat or further for recovering heat from waste.Preferably, the pressure variation device is according to the firstaspect.

According to an advantageous embodiment according to either one of theaspects shown above, the intermediate electric power device comprises arotor and a stator, both being separated by a hermetic sleeve. Indeed,for environmental reasons, provision is made for a device which ishermetically sealed by means of a hermetic sleeve between the rotor andthe stator of the motor/generator and preferably with a different casingfor each of the transmission cases of the scroll stages, which providesmore flexibility in selecting operating fluids (water, corrosiverefrigerant fluid, and/or inflammable fluids without any leak) as wellas for protecting the stator.

According to an advantageous embodiment in accordance with one of theaspects shown above of a scroll, device, the second stage is modular,selected from a second pressure variation device, a rotary device or alid. Such a modular device is capable of operating as an expander or asa compressor for controlling or treating a wide range of fluids ormedia) with high temperature and pressure ratios. The device consists ofone or two scroll stages (or modules) which are directly coupled with ashaft at both ends of a simple electric motor or generator. In thetwo-stage configuration, both modules may be connected in a paralleloperating mode according the required capacity and volume or in a seriesmode in order to operate at low and high pressures. The fluid may eitherbe treated or not between both stages. In the one-stage configuration,one end of the motor/generator is connected to an auxiliary pump deviceor sealed off by a lid.

According to another aspect, the present invention relates to the use ofa scroll device in a series configuration or an expander-pumpconfiguration, in a hybrid motor vehicle for producing electricity byrecovering heat from thermal waste (exhaust gases and/or from the engineblock) of the vehicle.

According to another aspect, the present invention relates to the use ofa scroll device in a series configuration or expander-pumpconfiguration, for the combined production of electricity and heat bymaking use of the value of fossil or renewable energies or furtherrecovering heat from thermal waste in industry.

BRIEF DESCRIPTION OF THE DRAWINGS

Other characteristics and advantages of the present invention willbecome more clearly apparent upon reading the detailed description whichfollows of the embodiments of the invention given as examples which areby no means limiting, and illustrated by the appended drawings, wherein:

FIG. 1 illustrates a pressure variation device according to a preferredembodiment;

FIG. 2 illustrates a pair of fixed and mobile scrolls;

FIG. 3 illustrates the mobile scroll fittings according to a preferredembodiment;

FIG. 4 illustrates a sectional view of the mobile scroll fittings;

FIG. 5 illustrates a widened sectional, view of the mobile scrollfittings according to another alternative embodiment;

FIG. 6 illustrates a scroll device with two high pressure ratio expanderstages;

FIG. 7 illustrates the radial positioning system of a scroll stageaccording to a preferred embodiment;

FIG. 8 illustrates the anti-rotation system of a scroll stage accordingto a preferred embodiment;

FIG. 9 illustrates the generator positioned between both stages.

FIG. 10 illustrates a scroll device with an expander stage and a stageequipped with a pump device.

DETAILED DESCRIPTION OF THE INVENTION

in the following description of the scroll device according to thepresent invention, for reasons of convenience, reference will primarilybe made to a configuration with one or two expander stages, except forFIG. 10, wherein the second stage comprises a feed pump. However, it isclear that each stage of the scroll device which represents a scrollmodule may operate either as an expander or as a compressor. It willalso be understood that it is possible to have a configuration with asingle stage possibly coupled with an electric device, the module alonebeing able to be used as an expander or a compressor. For this purpose,it will be further noted that the second stage is preferably modular,i.e. interchangeable, so as to allow a modification of the operation ofthe device. However, alternatively, the second stage may be integralwith the remainder of the device, i.e. non-modular.

The present description will now be provided as non-limiting examples inconnection with FIGS. 1 to 10.

FIG. 1 illustrates a pressure variation device as a scroll device whichmay be considered as a stage, here an expander stage. The expander stageis delimited by a scroll case 11. It contains a pair of scrolls 12, 13by which the gas (coolant) is expanded. The high pressure as isintroduced through the admission A into an open admission chamber 14 inthe pair of scrolls. By the orbiting movement of the mobile scroll 13with respect to the fixed scroll 12, the volume of the chamber increasesand provides the gas at a lower pressure in the discharge volume orchamber 15 after its pressure energy has been used for displacing themobile scroll. The contact between the mobile scroll and the fixedscroll is maintained by the axial positioning system consisting of anaxial bearing disk or plate 16 and of axial bearing segments 17, 18, onthe one hand, and by the radial positioning system for exampleconsisting of a crankshaft 19 and of a connecting rod 20 on the otherhand. The movement of the mobile scroll is maintained in translation byan anti-rotation system primarily consisting of an Oldham ring 54.

The fixed scroll 12 is attached to the scroll case 11 in the axialdirection by a rear ring 22, in the radial direction by the rear housing23 and in the angular direction by a positioning pin 24 positioned inthe scroll case 11 and the fixed scroll 12. A portion of the rearsurface 57 a of the fixed scroll is not in contact with the scroll case11 and forms a useful space 25 in terms of thermal insulation betweenboth parts. The fixed scroll 12 and the mobile scroll 13 have a sizesimilar to that of the basic disks 26 a, 26 b respectively. Theirsimilar geometries provide the condition for similar deformations andare used in order to reduce the clearances between both of these parts.The basic disk 26 a of the fixed scroll has an admission port 27 throughwhich the high pressure gas flows into the central open volume of thescroll, i.e. the open admission chamber 14.

Each of the scrolls 12, 13 respectively, therefore consists of a basicdisk 26 a, 26 b respectively, and of a scroll involute 39 a,respectively 39 b. As this is illustrated as a section in FIG. 2, ascroll involute 39 a combined with its counter-scroll 39 b form chamberswith increasing sizes 28. The movement of the mobile scroll relativelyto the fixed scroll implies that the gas moves in the chambers 28,increasing their volume by a factor defined as an installed volume ratio(VRi) until the peripheral chamber 29 is opened to the discharge chamber15 of the scroll case 11. Considering again FIG. 1, the fixed scroll 12has a peripheral contact ring 30 on which the basic disk 26 b of themobile scroll 13 slides during rotation. This, prevents the mobilescroll 13 from tilting over because of the radial torque of theresulting forces exerted on the mobile scroll.

FIG. 3 illustrates the fittings of the mobile scroll 13 which drive theradial positioning system into the direction of rotation by means of anorbiting bearing 41. The interface between the mobile scroll and theorbiting bearing is subject to thermal and mechanical deformations. Inorder to reduce these thermal deformations, detrimental to theefficiency of the device, it was noticed that high temperatureconditions promote heat exchanges with the coldest portions. It istherefore important to control heat transfer in order to avoid losses,but also to reduce thermal gradients in the parts which have significantgeometrical tolerances, and more particularly here the volutes, i.e. thescrolls. Hence, the latter need to be particularly well heat-insulated.To this end, several ingenuities are advantageously provided. Forexample:

i) Provision is made for separating the fixed volute 12 from the maincase 11 and for having two volutes 12 and 13 in the same geometricconditions and formed in identical materials so that the deformationsare similar.

ii) Provision may be made for a tolerance ring 42, consisting of abushing with a flexible radial thickness obtained by means of structurelayers (for example flexible 3-dimensional swirls or strips) with a verysmall sectional surface, this ring being placed between the housing ofthe orbiting volute and the outer diameter of the orbiting bearing 41.Spaces 43 are filled with air, gas vapor or low heat conductivityliquid, between the structured layers of the tolerance ring 42 and theouter diameter of the orbiting bearing 41 and between the layers and theinner surface of the housing of the mobile scroll. These spaces provideheat insulation between the mobile scroll and the orbiting bearing. Theflexibility of the tolerance ring 42 is used in order to maintaincontact and transmit radial forces between the mobile scroll 13 and theorbiting bearing 41, to the extent that their differences in temperatureand material properties cause their contact surfaces to expand accordingto various sizes.

iii) Provision may further be made, as illustrated in FIG. 4, for a thinseparation component, for example as a separation disk 44 which may beplaced at the bottom of the orbiting bearing 41 which separates themobile scroll 13 from the rotating bearing by a space 45 filled withair, gas, vapor or low heat conductivity liquid, such as lubricatingoil, by which heat transfer may be reduced from the mobile scroll 13right up to the orbiting bearing 41.

iv) As an alternative, as illustrated in FIG. 5, the equivalent effectmay be obtained by means of a disk filled with an insulating material 46by which heat transfer may be reduced from the mobile scroll 13 right upto the orbiting bearing 41.

v) Thermal insulation between the parts of the scroll stages and thetransmission system is provided by an insulating disk or a plate forinsulating the scrolls, 60 (FIG. 1) placed between the scroll case andthe transmission case 70 (FIG. 9). In order to reduce heat transfer fromthe expansion chambers to the transmission case as much as possible, theplate for insulating the scrolls (i.e. an insulating disk) extends fromthe outer diameter of the cases to the internal mobile parts. Accordingto this alternative embodiment, the outer diameter of the insulatingdisk is of the same size as the outer diameter of the cases; thus, thereis no direct contact between the cases. Centering screws and pins areused in order to maintain these three components blocked. According toanother alternative embodiment the insulating disk has a reduceddiameter and the positioning of the scroll case is directly fixed to thecontact of the transmission case.

vi) Thermal insulation between the expansion stage and ambient air isprovided by positioning any kind of insulating material around theexternal envelope of the scroll and the transmission cases which has theeffect of reducing thermal losses detrimental to the performances of theexpander and to the heat cycle.

Whatever the alternative considered among those shown in FIGS. 3, 4 and5, again considering FIG. 1, the front contact surface 48 and the crestsurface 49 of the mobile scroll 13, as well as the rear contact surface57 b between the mobile scroll 13 and the axial bearing 16 need toremain as flat as possible in order to reduce the clearances andpressure losses. Another means for reducing these deformations, apartfrom those shown earlier, consists of predicting the main deformationsand compensating them by thermal expansion devices which deform in a wayopposite to the scroll. Such an optional device, illustrated in FIG. 5,for example comprises a thermal expansion ring 47. Thus, while thetemperature rises, the ring 47 with a lower thermal heat conductionexpands more than the mobile scroll 13 and introduces a local forcewhich deforms this scroll in the direction opposite to the normaldeformation direction due to the heat transfer in the axial direction.

It will also be noted that it is possible to use the fluid forlubricating the volutes for transferring heat to the operating fluidbeing processed. The reduction in the temperature difference is afunction of the oil concentration, which contributes to reducing thermaldeformations advantageously.

Such a scroll device comprising one or more of these ingenuities enablesthe use of a high temperature fluid and a reduction of the thermallosses and clearances when the electric device (a motor or generator) iscooled ensuring efficient operation of the device.

Considering FIG. 6, a scroll device with two high pressure ratioexpander stages is illustrated. The components of the scroll device aredescribed in a configuration involving two expander stages coupled witha simple generator G placed in the middle forming a high pressure ratioexpander. A first HP stage of the expander operates at a high pressurelevel and the second LP stage of the expander operates at a low pressurelevel. In this example, the stages of the expander are directly coupledwith the shaft of the generator. The high pressure gas enters the HPstage of the expander through the admission A and exits through theoutlet B as visible in FIG. 6. Next, the gas may either be treated ornot through an optional treatment device P before it enters the LP stageof the expander through the admission C and exits the LP stage throughthe outlet D. The expansion work of both stages is transmitted to thegenerator by the movement of the mobile scrolls on each of the expanderstages, transformed into a rotary motion by an eccentric mechanismcoupled with a shaft common to both stages. In the generator G, therotor is mounted on the shaft and transforms the mechanical transmissioninto an electric current through the stator. As a general expression onecould refer to a dynamoelectric machine encompassing such generator andmotor.

Such a high pressure ratio application is possible thanks to the seriesconfiguration of both HP and LP expander stages, including the admissionand outlet ports of which A, B, C and D through which the operatingfluid travels in this order. It will be noted that in this advantageousembodiment of the present invention, the admission ports A and C aredecoupled from each other, and in the same way the outlet ports B and Care also decoupled from each other.

It will further be noted that heat cycles provide better efficiencies ata high pressure ratio (of the order of 10 to 30), whereas conventionalturbines or expanders with a volume ratio VRi (2-4) have lowefficiencies for this order of pressure ratio magnitude. For a questionof cost and bulkiness, the size should also be reduced, or the powerdensity of the turbine should also be increased, it is therefore ofinterest to operate at a high speed. Thus, the device should beseparated into two stages, which provides an installed volume ratio(VRi) greater than 12 and a possibility of operating at speeds between1,500 and 6,000 rpm. However, in order to reduce the costs of theelectronics and parts, the assembling of two turbine stages, i.e.expanders, is carried out on a same generator, which also allows thenumber of bearings to be also reduced. Within the scope of the presentinvention, a particularly advantageous VRi distribution selection wasrevealed so that the dimensions of a stage are not a penalty to thespeed of the whole of the device, but on the contrary so that bothstages reach the same speed limits. This selection corresponds to stageswith similar outer diameters, for this, the VRi of the first stage isselected to be much higher than that of the second stage.

Both expander stages are preferably of identical construction, theirdescription having been given in detail earlier in connection withFIG. 1. An expander stage as illustrated, in FIG. 1 is again consideredhereafter.

in order to maintain the contact between the mobile scroll and the fixedscroll, an axial positioning system and a radial positioning system areprovided, which were briefly discussed earlier and which will now bedescribed in more detail. The axial positioning system, as illustratedin FIG. 1, mainly consists in two ring segments 17, 18, urged againstthe rear contact surface 57 b of the mobile scroll 13, defining, betweenthem a chamber 31 which may be pressurized with a fluid originating fromthe outside or inside. The pressure of the fluid against the rearcontact surface 57 b provides the axial force on the mobile scroll 13which maintains it in contact with the fixed scroll 12. The ringsegments 17 and 18 are inserted in a ring groove formed in the axialbearing disk 16, with segment gasket seals 32, 33 on the inner and outersides, allowing the segments to move in the longitudinal direction andto provide axial conformity. The upper surface of the ring segments arepreferably formed with a material having good wear resistance. The ringsegments 17 and 18 are kept in contact with the rear contact surface 57b by means of the pressure difference on either side of the surfacedefined by the sealing diameter on the gasket seal and the sealingdiameter on the upper surface of the ring, segment. Under initialconditions, the contact between the segments 17 and 18 and the rearcontact surface 57 b is maintained by means of an arrangement of springs34 of the axial bearing on the ring segments, providing a minimum forcein the direction of the mobile scroll 13, sufficient for overcomingstatic friction between the segment joints 32, 33 and the sides of thering groove.

The function of the radial positioning system is to maintain the mobilescroll in radial contact with the fixed scroll, because the pressure inthe scroll chambers tends to separate the latter, in order tocounterbalance the centrifugal force of the mobile scroll and totransmit the displacement force of the mobile scroll as a torque to theshaft of the generator. There are several ways for providing thesesfunctions. In the preferred configuration illustrated in FIG. 7, thetangential component Ft of the resulting pressure forces FD applied onthe orbiting bearing is transferred to a crankshaft 19 by traction oralternatively by compression of a connecting rod 20, pivotably mountedon the crankshaft by the crank pin 36. The connecting rod is affixed tothe mobile scroll through the orbiting bearing mounted on the orbitingcrank pin 37. The counterweight 38 bound to the connecting rod 20 isdesigned so as to balance the centrifugal force Fc caused by theorbiting part. The tangential component of the force applied on thecrankshaft is transmitted as a torque by the crankshaft attached to theshaft of the generator and is thus transmitted to the generator. Thedirection of the reaction force Freac of the connecting rod on theorbiting bearing is determined by the angular arrangement of thecrankshaft 19 and of the connecting rod 20; from there, appears anoutward-directed radial force Frad, related to a given driving force. Byproperly selecting the angular arrangement, the radial force value mayexceed the radial component Fr of the driving force Fd which tends toseparate the fixed scroll from the mobile scroll and may thereby providethe radial contact between the scrolls. The arrangement of thecrankshaft and of the connecting rod provides a radial positioningsystem with the required radial conformity.

FIG. 8 illustrates the anti-rotation system integrated into a scrollstage as detailed in FIG. 1. The upper surface of the axial bearing disk16 has two radial grooves 50, 51 (FIG. 1) diametrically opposite to eachother and formed in the disc in order to be used as grooves forcorresponding keys 52, 53 (FIG. 8) also positioned oppositely andlocated on one side of the Oldham ring 54. The external rear surface 57b (FIG. 1) of the basic disk of the mobile scroll has similar radialgrooves diametrically opposite to each other and which are spaced out by90° relatively to the grooves 50, 51 of the axial bearing disk 16. Thesegrooves are used as grooves for the corresponding keys 58, 59 (FIG. 8)positioned on the other side of the Oldham ring 54. The purpose of theOldham ring is to maintain the fixed and mobile scrolls in apredetermined set angular relationship.

FIG. 9 illustrates the generator positioned between both stages of thedevice of FIG. 6. The shaft 71 of the generator transmits the mechanicaltorque into a magnetic torque by means of synchronous or asynchronousdevices of the rotor 72 and of the stator 73, which subsequently produceelectric current, useful for providing an electric network or forstoring energy in batteries. The shaft 71 is mounted in the inner ringof two radial bearings 74, 75 attached in the transmission cases 70, oneither side of the generator. The expansion volume on each stage isaxially insulated from the rear surface of the orbiting scrolls by meansof an axial bearing disk and an axial bearing ring. Thus the pressure inthe transmission cases is different and independent of the pressure inthe volutes, allowing independent stages to operate separately or in aseries operating mode, as illustrated in FIG. 1, so as to be able toexpand or compress an operating fluid with a very high pressure ratio,or in a parallel operating mode in order to be able to expand orcompress one or simultaneously two operating fluids under differentconditions.

Lubricating oil is introduced into the shaft through a conduit 76,formed in the transmission cases, internal shaft seals 77 with lowfrictional losses and withstanding high temperatures are positionedbetween the transmission cases and the shaft.

Referring to FIG. 1, lubricating oil is conveyed right up to theorbiting bearing 41 and to the crank pin 36 by means of passages formedin the crankshaft 19 and the connecting rod 20. The lubricating oil iscollected at the bottom of the transmission cases 70. An external orinternal oil pump delivers the collected oil at a high pressure into theadmission of the lubricating system. Additional gasket seals may beplaced on the shaft for better medium separation between the fluid usedin the high pressure HP stage and the fluid used in the low pressure LPstage, if they differ. The preferred arrangement is to have a singlepressure level in both transmission cases and in the generator, in orderto have only a single oil pump discharge pressure and no axial force dueto the pressure differences on the shaft. The advantageous use of alubricating circuit at a single pressure instead of two systems withdifferent pressures will be noted here.

Again referring to FIG. 9, equalization holes 80 are provided in thetransmission case for the pressure balance between the transmission case70 and the generator case 86. The stator 73 is mounted in the generatorcase by radial damping. The heat produced by the stator is transferredby conduction to the generator case 86 and then evacuated to the ambientair through the external surface 81 with fins of the generator case ortowards a forced convection cooling system. The gasket seals 82 are usedbetween the generator case 86 and the transmission cases 70, between thetransmission case and the insulating disk of the expander, both betweenthe insulating disk and the scroll case. A hermetic sleeve 83 mayadvantageously be placed between the rotor 72 and the stator 73 ifcorrosive fluids are used, in order not to damage the stator. Thisprotection of the stator may be achieved by a glass fiber partition,passing between the rotor and the stator, no shaft seal is used forthis. The hermetic sleeve 83 is radially sealed on its ends by means ofa radial seal 84 located in a groove of a cylindrical housing 85 eitherconnected to the back of the transmission case 70 or to the innerdiameter of the generator case 86. All the gasket seals 82 and 84 may bereplaced with welds providing total sealing of the system.

In the alternative modular design of the second stage of the device asshown in FIG. 6, the system may also operate in a configuration with oneor two stages. Thus for example, in a single stage configuration, theside of the generator which is not connected to a stage of the expandermay be equipped with any rotating device which would need mechanicalpower, such as a pump stage, as illustrated in FIG. 10, or a compressorstage. It may alternatively be connected to a lid so that the device isconverted into a single stage expander.

As mentioned, FIG. 10 illustrates a scroll device with an expander stageand a stage equipped with a rotating device, in particular a pump stage.The expander stage comprises a scroll case containing a fixed scroll anda mobile scroll relatively to the case and with admission and outletports for the fluid to be expanded.

It is thus obtained a scroll device comprising two coupled stages T andP on a rotary shaft, at both ends of an intermediate electrical powerdevice G, wherein the first stage is formed by a pressure variationdevice T (i.e. here an expander) of an operating liquid, comprising ascroll case containing a fixed scroll and a mobile scroll relatively tothe case, and with admission A and outlet B ports, and characterized inthat the second stage is a supply pump P which pumps the operatingliquid and provides it in return.

The expander preferably comprises means for thermally insulating thescrolls. These thermal insulation means are advantageously providedbetween the fixed scroll and the corresponding scroll case. When anorbiting bearing is provided, thermal insulation means may be alsoprovided between the mobile scroll and the orbiting bearing, maycomprise a separation disk placed at the bottom of the orbiting bearingwhich separates the mobile scroll from the rotating bearing by aninsulation space and may also comprise an insulating material placedbetween the orbiting bearing and the mobile scroll. Additionally meansfor preventing thermal deformations of the scrolls may be provided.These means for preventing thermal deformations are advantageouslyformed by an expansion ring introducing a local force which deforms themobile scroll of the corresponding stage in the direction opposite toits normal deformation direction.

As for the scroll devices presented hereinbefore, wherein theintermediate electric power device G comprises a rotor and a stator, ahermetic sleeve may be provided between the rotor and the stator.Further each stage may be confined in a hermetic casing.

Referring back to FIG. 10, the arrangement of a pump P coupled with theturbine T, i.e. the expander stage, and with the generator G is ofparticular interest when the device is organized in a Rankine cycle forproducing electricity, in which all the mobile components are confinedin a hermetic casing. By a Rankine cycle, is meant a theoreticalthermodynamic cycle used in steam engines including at least four mainsteps: i) pressurized liquid vaporization; ii) vapor expansion; iii)vapor condensation; iv) pumping liquid again to the initial pressure.

Such a configuration is described in FIG. 10, wherein a vapor generatorS provides through the admission port A of the expander T, a pressurizedliquid, which is expanded and then transmitted from the outlet port B toa condenser K feeding a pump P pumping the liquid to the initialpressure and providing it to the vapor generator S through an outletport S.

A two-stage device in a series configuration or in an expander pumpconfiguration as described in connection with FIGS. 6 and 10respectively is advantageously integrated into an automotiveapplication. Such a device allows electricity to be produced onboard ina hybrid motor vehicle by recovering heat from the waste exhaust gas, ofthe engine.

It is also possible to integrate such a device into an application forcombined production of electricity and heat. Preferably such aproduction of electricity and heat will be obtained by making the mostof the value of renewable energies or the value of thermal waste inindustry.

It will be understood that various modifications and/or improvementsobvious for one skilled in the art may be made to the differentembodiments of the invention as described in the present descriptionwithout departing from the scope of the invention as defined by theappended claims.

1. A device for varying pressure of a fluid, comprising a scroll casecontaining a fixed scroll and a mobile scroll relatively to the case,and with admission and outlet ports for the fluid, an orbiting bearingand means for thermally insulating the scrolls, wherein these thermallyinsulating means include the fixed scroll being separated from thescroll case and a tolerance ring, consisting of a bushing with aflexible radial thickness, being placed between a housing of the mobilescroll and the outer diameter of the orbiting bearing.
 2. The pressurevariation device according to claim 1, wherein the thermal insulationmeans are provided by a space between the fixed scroll and thecorresponding scroll case.
 3. The pressure variation device according toclaim 1, wherein the thermal insulation means are also provided betweenthe mobile scroll and the orbiting bearing.
 4. The pressure variationdevice according to claim 1, wherein the thermal insulation meanscomprise a separation disk placed at the bottom of the orbiting bearingwhich separates the mobile scroll from the rotating bearing by aninsulation space.
 5. The pressure variation device according to claim 1,wherein the thermal insulating means comprise an insulating materialplaced between the orbiting bearing and the mobile scroll.
 6. Thepressure variation device according to claim 1, wherein means forpreventing thermal deformations of the scrolls are provided.
 7. Thepressure variation device according to claim 6, wherein the means forpreventing thermal deformations are formed by an expansion ringintroducing a local force which deforms the mobile scroll in thedirection opposite to its normal deformation direction.
 8. A scrolldevice including two coupled stages on a rotary shaft, at both ends ofan intermediate electric power device, wherein the first stage is formedby a first pressure variation device according to claim 1, and whereinthe second stage is formed by a second pressure variation device withsecond admission and outlet ports respectively decoupled from theadmission and outlet ports of the first pressure variation device. 9.The scroll device according to claim 8, wherein the first stage isattached in a scroll case and a transmission system is attached in atransmission case, and wherein thermal insulation means are providedbetween the stage and the transmission system, in the form of aninsulation plate placed between the scroll case and the transmissioncase.
 10. The scroll device according to claim 8, wherein the secondstage is connected in a series configuration to the first stage so thatone of the two stages operates at a higher pressure than the other. 11.The scroll device according to claim 8, wherein the second stage isconnected in a parallel configuration to the first stage, so that bothpressure variation devices are independent from each other.
 12. Thescroll device according to claim 8, wherein the intermediate electricpower device comprises a rotor and a stator, and wherein a hermeticsleeve is provided between the rotor and the stator.
 13. (canceled) 14.The use of an apparatus according to claim 8, in an hybrid motor vehiclefor producing electricity by recovering heat from waste exhaust gas ofthe engine of the vehicle.
 15. The use of an apparatus according toclaim 8, for combined production of electricity and heat.